An emergency telephone number alerting and guidance process to guide emergency responders to the exact scene of an emergency declared by dialing the emergency services notification (ESN) telephone number consisting of the following steps: a decoder detecting the ESN telephone number as it is dialed on...http://www.google.com.hk/patents/US5960061?utm_source=gb-gplus-share專利 US5960061 - Emergency telephone number alerting device
